Synthesis and characterization of a series of gold(III) complexes with the 4,4′-dimethyl-2,2′-bipyridine ligand: Counterion influence on the cytotoxicity of gold(III) complexes

A series of Au(III) complexes, [Au(4,4′-dmbipy)X2]+Y− where X = Cl, Br and Y = [AuCl4], [AuCl2], [ClO4], [AuBr4], were prepared from the reactions of HAuCl4·3H2O/AuBr3 with 4,4′-dimethyl-2,2′-bipyridine (4,4′-dmbipy) in a mixture of alcohol/CH3CN. These complexes were characterized by elemental analysis, IR, UV–Vis, 1H and 13C NMR spectroscopy and their structures were studied by the single-crystal diffraction method. The electrochemical behavior of the title complexes were also studied in CH3CN and DMSO using cyclic voltammetry. The cationic parts of the complexes are similar, with a bidentate nitrogenous 4,4′-dmbipy ligand and two halide anions attached to a gold(III) center in a square-planar geometry. However, the effect of the anionic parts of the complexes on the cytotoxic properties was evaluated in four cultures, Vero, A431, HeLa and HT-29 by means of an MTT assay. The results illustrate that the anion part plays an important role in the cytotoxicity of relevant compounds in different cell lines. Complexes 1 and 4, with the similar anion part of [AuX4]− (X = Cl and Br), displayed good agreement in their anticancer activities toward human cancer cell lines.

Graphical abstractA series of Au(III) complexes, [Au(4,4′-dmbipy)X2]+Y−, where X = Cl, Br and Y = [AuCl4], [AuCl2], [ClO4] and [AuBr4], were prepared and structurally characterized by spectral and X-ray diffraction methods. These complexes were used for in vitro cytotoxicity evaluation against in four cultures. The results illustrated that the anionic parts in these complexes play an important role in the cytotoxicity of the compounds against the different cell lines.Figure optionsDownload full-size imageDownload as PowerPoint slide